Does NSD delay re-opening of its log file?

I've observed something strange on some of our busy servers. Logrotate
reports something like this:

/etc/cron.daily/logrotate:

gzip: stdin: file size changed while zipping

So here's what logrotate does:

1. mv nsd.log nsd.log.old

2. runs "nsd-control log_reopen"

3. gzip nsd.log.old

Occasionally, when performing step 3, gzip complains that the input file
size changed, meaning that NSD was still writing to it.

Is it possible that NSD delays re-opening of the log file?

Regards,
Anand